Lyme disease is caused by the spirochete Borrelia burgdorferi, a gram-negative bacterium transmitted to animals and humans by infected ticks of the Ixodes genus. Lyme disease is characterized by the presence of the classic bull's-eye rash surrounding the tick bite, erythema migrans, accompanied by nonspecific symptoms such as fever, malaise, fatigue, headache, and myalgia. B. burgdorferi infection in the untreated or inadequately treated patient may progress to disseminated disease. Manifestations of disseminated disease occur in two phases. The first phase occurring days to weeks after infection includes neurological symptoms and/or cardiac dysfunction, while the second phase occurring weeks to months after infection includes arthralgias and arthritis.
Lyme disease has rapidly emerged as the most prevalent zoonotic vector-borne infectious disease in the United States, and its geographical range is expanding. In 2002, nearly 24,000 cases of Lyme disease were reported to the Centers for Disease Control and Prevention (MMWR, 52:741-750, 2003), and more than 150,000 cases have been reported to U.S. health authorities since 1982, when a systematic national surveillance was initiated. The regrowth of natural forests from farmland in the Northeastern United States in the twentieth century has created conditions conducive to the spread of human Lyme disease. Suburban communities are now often adjacent to forested areas where Ixodes scapularis populations thrive along with deer (Odocoileus virginianus) and white-footed mice (Peromyscus leucopus), known to be the major natural reservoir for B. burgdorferi. Methods to control B. burgdorferi through acaricide or antimicrobial agents are limited and many, such as organochlorine pesticides, have had negative environmental and human health effects sufficient to outlaw their use.
The development of a highly specific, easily distributable, economically viable wildlife vaccine to be used to reduce the prevalence of B. burgdorferi in ticks and in animal reservoirs surrounding human communities could quickly and significantly reduce the incidence of Lyme disease cases. Such a vaccine would also be desirable for use in domesticated animals including species of agricultural importance, as well as species kept as pets.
Additionally, an oral Lyme disease vaccine for human consumption would be a pleasing alternative to traditional intramuscular or intradermal vaccines, for preventing human morbidity associated with bites from B. burgdorferi-infected ticks.